Duty assessment for warehoused imports secures liability by bond; duty payable on ex-bond filing at prevailing rate. A separate Bill of Entry for Warehousing is used; assets are assessed and duty determined at warehousing to secure liability by execution of a bond since payment is deferred. Duty is paid on ex-bond clearance when an Ex-Bond Bill of Entry is filed, and the applicable rate is the rate in force on the date of filing the Ex-Bond Bill of Entry.